Condylar Fracture Fixation System

ABSTRACT

A condylar fracture fixation system for use with an intramedullary nail includes a longitudinally extending rod having first and second ends, each end having outwardly extending threads or ridges. The rod extends along a first longitudinal axis which extends in a medial-lateral direction in use. A first and second nut is provided each nut having first and second ends. The second end of each nut having an opening formed by a plurality of resilient legs for respectively receiving the first and second ends of the rod. The second end of the first and second nuts include ridges or threads extending into the opening in each nut. The inwardly extending ridges of nuts respectively engaging the outwardly extending threads or ridges of the rod. A flexible washer is connected to the first end of each nut.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 14/640,456, filed on Mar. 6, 2015, the disclosure of which ishereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a supra condylar intramedullary nailfor the femur. More particularly it relates to an intramedullary nailusing a novel condylus screw having two threaded nuts or two nuts havinga ratchet system and a flexible washer mounted on the nuts.

In treating a femoral fracture, it is standard practice to use afixation device adapted to facilitate recovery of the fractured bone.The fixation device provides immobilization of the bone fragments andstabilization of the fractured femur, thus providing earliermobilization and weight bearing of a patient. The fixation device isattached to or inserted into the femur and cooperates with the bonefragments and the femoral shaft to stabilize the bone. As the boneheals, the fixation device allows the bone fragments to compress intoeach other so the fragments grow together to restore the bone.

Two prevalent types of femoral fractures are supracondylar or “T-type”condylar fractures about the distal femur. A number of differentfixation devices, both external and implantable, have been devised forfixation of supracondylar and condylar fractures. In the past, treatmentof condylar or supracondylar fractures consisted of stabilizing the boneportions with plates and screws. However, in using plates and screws,invasive surgery is required and includes considerable dissection of thethigh in order to expose the fracture so as to attach the plates andscrews. The resultant devasculariztion of the distal portion of thefemur has lead to a high frequency of complications of delayed union ofthe bone sections, osseous fracture and infection. Additionally, due tothe muscular stresses in the region of the condylus and supracondylus,the treatment may involve undesirable post-operative procedures andcomplications including the bending or breaking of the plates, looseningof the screws and migration of the femoral shaft.

Intramedullary (IM) nailing has become a standard procedure for treatingsupracondylar and condylar fractures. In its basic form, IM nailingconsists of driving a rod-like nail into the intramedullary bone canalof the femur to stabilize transverse fractures of the femur. To furtherstabilize the bone fragments interlocking cross-bolts or screws throughthe nail that are fixed on both sides of the fracture are used.

Known IM nails have been designed for treatment of condylar andsupracondylar fractures. U.S. Pat. No. 6,010,505 Asche et al., thedisclosure of which is herein incorporated by reference in its entirety,discloses an intramedullary device having an IM nail and interlockingbolts or screws to grip and stabilize the femoral condyles with respectto the femoral shaft.

In Femoral fractures involving the femoral condyles (e.g. T-condylarFractures), an IM nail is currently used in combination with a StrykerTrauma T2 condyle screw (shown in FIG. 1A (prior art)) in order torealign, compress and fix the femoral condyle fracture fragments. Theexisting condyle screw system consists of one 5 mm diameter screw with afirst pre-assembled 15 mm diameter washer at the level of the screw head(the washer position is fixed to the screw adjacent the head in a mannerin such that it is free to rotate in all directions). A second nut witha pre-assembled 15 mm diameter washer mounted thereon can threadablyengage threads on the end of the screw opposite the head, (the washerposition is fixed to the nut, but again, it is free to rotate in alldirections).

In the prior art design once the screw is completely inserted into thebone medially, the nut is then screwed onto the screw laterally, acompression force will be generated between the washer and the bonecortex from both sides (lateral and medial). This compression forcefixes the bone fragments. All the components (screw, nut, washers) arepreferably made out of a titanium alloy, preferably grade 5. When theprior art condyle screw is used on an irregular-shaped-surface of thedistal femoral condyles, the washers might not properly adapt to thecortical surface. As a result, the washer might protrude out the bonesurface and impinge to the biological tissue. The impingement mayinvolve the knee joint cartilage surface, generating pain, inflammationor even damage to the tibial plate cartilage. Furthermore the procedureto compress the fragments is time-consuming since many screw turns needto be carried out in order to achieve the contact of both washers (fromboth sides) to the bone cortex.

BRIEF SUMMARY OF THE INVENTION

In the preset invention, a condylar fracture fixation system includes anintramedullary (IM) nail which, after insertion into the femur extendsin a proximal-distal direction. A condylar screw system includes alongitudinally extending rod which has first and second ends with eachend having outwardly extending threads or ridges. The rod extends alonga first longitudinal axis extending in a medial-lateral direction wheninserted through the femoral condyles and the IM nail.

A first and second nut each having first and second ends are provided.The second end of each nut has an opening for respectively receiving thefirst and second ends of the rod. The second end of the first and secondnuts include threads or ridges extending radially inward into an openingin each nut. The inwardly extending threads or ridges of the first andsecond nuts respectively engaging the outwardly extending threads orridges of the rod first and second ends. Preferably the first end ofeach nut is a cylindrical body having two, three or over four legsextending towards the second end of each nut. At least two of the legshave threads or ridges extending into the opening of each nut.

A flexible washer engages the first end of the first and second nuts.Like the prior art screw, the washers are axially fixed to each nut in amanner which permits rotation about the rod longitudinal axis. Theradially outwardly extending threads of the first and second rod endsmay be formed as a helical thread. The radially inwardly extendingthreads of the first and second nuts may also be formed as helicalthreads. The flexible washer and nut may be a one-piece construct or maybe separate but connected in a manner which allows the washer to rotatearound the axis of the nut. This may be accomplished by allowing thewasher to snap into a circumferential groove formed at the outer surfaceof the first end of the nut. The nut and washer may be made of amaterial selected from the group consisting of a polymeric material,titanium, a titanium alloy and stainless steel. The flexible washer maybe made of metal (Titanium) having a thickness of 1 to 3 mm.

The first and second nuts preferably have a body portion at the firstend with a plurality of legs extending outwardly therefrom towards thesecond end. The legs surround a central opening for receiving thethreaded rod. The ridges or threads are located on inner surfaces of thelegs. The nut body portion may be threaded into the threaded rod or ifridges are present, or may be moved axially onto the rod withoutrotation since the two, three or four legs are designed to flexoutwardly. Thus the nuts can slide over the threads or ridges on eachend of the nail for example, as in a ratchet system. The flexible orbendable washer may be non-circular such as having two diametricallyopposed oval positions similar to a pair of oval opposed petals of aflower or leafs of a plant, or a two-blade propeller on a plane. Twoopposed pairs are preferred since minimum coverage of the bone ispreferred and using three or four “leafs” large enough to be effectiveteaches away from the medical need of “minimum coverage” at thecondlyes. Both washers, petal, and leaf portions are bendable by hand orwith a hand tool so that the surgeon can form-fit them to the patientcondyles.

One important aspect of this design is, that the washer surface isreduced to a minimum so it covers the bone only where needed and doesnot protrude outwardly.

The nut can have a body portion and the washer could be one piececonstruct manufactured as a molded plastic part, however, although asnap-filled metal washer (Titanium) is preferred.

If a one-part nut washer would be applied then the connection betweenthe washer opposed oval petals or leafs and the washer body would bepreferably made by injection moulding of plastic and alternatively laserwelding or glueing of metal.

Alternatively a two-part nut washer could also be formed by acirmcumferential groove on the washer body so that a washer with twoopposed petals or propeller wings can be clamped onto the washer bodyportion 38. This is how the prior art T2 Condyle Washer is assembled.

Alternatively the condylar fracture fixation system may not include anIM nail but also have a longitudinally medially-laterally extending rodhaving first and second ends. The first and second ends each having aplurality of radially outwardly extending protrusions such as ridges orthreads. First and second nuts are provided with each nut having ahollow interior open portion having an open free end for respectivelyreceiving the first and second ends of the rod. The interior portion ofthe first and second nuts having a plurality of recesses for receivingthe outwardly extending protrusions on the first and second ends of therod. A flexible washer is mounted on an end of each of the first andsecond nuts opposite the open end.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevation view of the rod of the present invention having apair of threaded ends;

FIG. 1A is an isometric view of the prior art condylar screw having anut, washer and a single threaded end;

FIG. 2 is a top view of the washer and nut combination of the presentinvention;

FIG. 2A is a top view of the washer and nut combination of FIG. 2showing the rotatability of two flexible portions mounted on the washerof the present invention;

FIG. 2B is a cross-sectional view of FIG. 2A along lines 2B-2B showingthe washer with the flexible washer portions rotatably mounted in agroove in the washer body;

FIG. 2C is a cross-sectional view similar to that of FIG. 2B, but withthe flexible washer portions integrally formed on the nut body such byinjection molding;

FIG. 3 is a cross-sectional view of the washer and nut combination ofFIG. 2 with flexible titanium washers welded onto the nut body;

FIG. 4 is a schematic view of a pair of nuts including the washers asshown in FIGS. 2 and 3 pressed or threaded onto the threaded ends of therod of FIG. 1;

FIG. 5 shows the two nut/washer combination elements fully seated on thethreaded ends of the rod of FIG. 1 compressing a condylar fracture in afemur;

FIG. 6 shows an isometric view of a distal femur with the condylar screwof the present invention compressing a condylar fracture;

FIG. 7 is an elevation view of the prior art condylar screw of FIG. 1Ashowing the possible fracture compression distance Δx; and

FIG. 8 shows the possible fracture compression distance 2Δx with thecondylar screw of the present invention.

DETAILED DESCRIPTION

Referring to FIG. 1 there is shown a threaded rod generally denoted as10 having a first and second threaded end 12 and 14. Rod 10 can be ofany length in diameter typically being a 5 mm diameter rod with avariety of lengths. Rod 10 forms the shaft of a condylar screw used tocompress fractures of the distal femur.

FIG. 1A shows a prior art condylar screw generally denoted as 10 ahaving a head 11 a formed at a first end of a shaft 16 a, having athreaded end 14 a. A nut 17 a has internal threads adapted to threadablyengage threads 14 a on shaft 16 a. Nut 17 a includes an enlarged headportion 18 a. A washer 20 a is attached to each head portion 11 a, 18 aand is free to rotate with respect to shaft 16 a. Washers 20 a are madeof metal and are not easily deformable.

Referring to FIGS. 2 and 3, there is shown a nut 18 and washer 20combination generally denoted as 30, which includes a nut body portion32 and two flexible portions 34 and 36. Preferably flexible washerportions 34 and 36 are in the shape of a flower petal or oblong shapespaced on opposite sides of nut 32, i.e. 180° apart. Three or four suchpetal-like flexible washer portions may be utilized spaced equidistantlyaround the circumference of nut body 32. Nut body 32 includes a solidbody portion 38 from which extends a plurality of legs 40. Preferably,there are four legs 40 as shown in FIG. 3, surrounding a hollow or openinterior 42 of nut and washer 30 designed to receive a threaded ends 12,14 of rod 10. Legs 40 have inwardly extending ridges or threads 44 whichengage with the thread of threaded ends 12, 14. The washer and nut 30may have two or three legs if desired. FIG. 3 shows a pair of titaniumleafs or pedal-like washer portions welded to a titanium nut body.

Referring to FIG. 2A, there is shown the nut washer combination of FIG.2 with two oval washer portions 34 a and 36 a rotatably mounted on nutsolid body portion 38 a. Also shown is a hex portion 39 a used to drivethe nut body 32 a onto the threaded rod 10.

FIG. 2B shows a cross-sectional view of FIG. 2A along lines 2B-2B withthe nut body 32 including a groove 35 for receiving inner ends of washerportions 34 a and 36 a. Preferably, portions 34 a and 36 a areintegrally formed on an inner ring-like portion which is received withina circumferential groove 35. At least a major portion of thecircumferential groove 35 extends around the nut solid body portion 38a. The ring may act as a snap ring by having part of the ring-likeportion open so that the open portion may be elastically made larger tofit and snap into the groove 35. Since the elastic deformation isresilient, the ring will snap into position, thus holding portions 34 a,36 a on nut body 32 a, but allowing the rotation thereof around thecircumference of the preferably cylindrical nut body 32 a. Preferably,the groove 35 is formed in the solid body portion 38 a intermediate thedrive portion 39 a and the legs 40 a.

Referring to FIG. 2C, there is shown a nut 32 b having a solid bodyportion 38 b, a drive portion 39 b, legs 40 b and a pair of integrallyformed washer portions 34 b and 36 b. Washer portions 34 and 36 b may beinjection molded along with the nut body 32 b. This embodiment may bemade of a polymer such as PEEK (polyetheretherketone). FIG. 3 shows atitanium nut 32 with a pair of titanium flexible portions 34 and 36welded to solid body portion 38. Obviously, the flexible portions 34 and36 do not rotate about the circumference of nut 32 in this embodiment.

Flexible washer portions 34, 36 are preferably coupled to nut solid bodyportion 38 by a snap fit connection. In the preferred embodiment, thewasher portions 34, 36 are made of titanium approximately 1 mm thick. Inthe preferred embodiment, the legs 40 are separated by slots 50, whichare approximately 1 mm wide and 4 mm long. Legs 40 are approximately 1mm thick and are able to flex outwardly upon engagement between teeth orridges 42 and the threaded ends 12, 14 of rod 10. While ridges 42 may beconcentric parallel protrusions extending into the hollow interior ofnut 30, such could be formed as helical threads.

Referring to FIGS. 4 and 5, there is shown the method of using thecondylar fixation system of the present invention which includesinserting rod 10 into the distal femur denoted as 100 across the medialand lateral condyles 102, 104. Typically, the fracture 106 occurs at theinter-condylar notch area 108 and extends proximally and laterally tothe medial condyle area 110.

As shown in FIG. 4, the pair of nuts and flexible portions 36 may beinserted from the medial and lateral sides of the distal femur intoengagement with the threaded portions 12, 14 of rod 10. This may be doneby applying an axial force as shown in FIGS. 4 and 5 pushing nuts 32 andflexible portions 30 onto the threaded ends of rod 10. Alternately, ifthe ends of rod 10 and the protrusions 44 of nut legs 40 are helicalthreads, nut and flexible portions 30 may be screwed onto position as atypical nut.

Referring to FIG. 5, there is shown nuts/flexible portions 30 in theseated position with legs 40 fully engaging threaded portions 12, 14 ofrod 10. In this position, oval washer portions 34 and 36 deform uponengagement with the outer cortex of condyles 102, 104 to match thesurface contour. Oval washer portions 34, 36 are mounted on nut body 32in such a manner that they may rotate about the central axes of the nutbut are fixed axially. Thus they may be positioned in anycircumferential orientation which allows oval portions 34, 36 to bestconform with the outer bone surface in the condylar area. The finalassembly is shown in FIG. 6 with the condylar screw of the presentinvention compressing fracture 106.

Referring to FIGS. 7 and 8, there is shown a comparison of thecompression range of the use of two nuts 30 on a threaded rod 10 of thepresent invention instead of a single screw as shown in FIGS. 1A and 7.The use of a pair of nuts 32 doubles the compression range Δx of FIG. 7to 2Δx of FIG. 8. As a result the condylar screw of the presentinvention will reduce the number of different screw lengths needed to bekept in inventory while ensuring the same working range.

The device of the present invention may be used for fracturestabilization in general where compression between implant and bone isdesired. For example, the device can be used in the proximal humerus forsmall fragments, osteoporosis and where there is a relatively thincortex where a washer is beneficial; the radius/ulna; the pelvis in thesacroiliac joint; the proximal and distal tibia; and the foot in thecalcaneous and charcot plate

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

1. (canceled)
 2. A fracture fixation system comprising: a longitudinallyextending rod having first and second ends, each end having ridgesextending in a radially outward direction; first and second nuts eachhaving first and second ends, the first and second nuts each having acavity extending from the second end toward the first end andterminating between the first and second ends for respectively receivingthe first and second ends of the rod, the second end of each of thefirst and second nuts including radially inwardly extending ridges forrespectively engaging the outwardly extending ridges of the first andsecond ends of the rod; and a washer having opposed bendable portionsengaging the first and second nuts.
 3. The fracture fixation system ofclaim 2, wherein the radially outwardly extending ridges of the firstand second rod ends are formed as a helical thread.
 4. The fracturefixation system of claims 3, wherein the radially inwardly extendingridges of the first and second nut are formed as helical threads.
 5. Thefracture fixation system as set forth in claim 2, wherein the flexiblewasher and nut are welded to another or formed as an integral monolithicconstruct.
 6. The fracture fixation system of claim 5, wherein thewasher and nut construct is made of a material selected from the groupconsisting of a polymeric material, titanium, a titanium alloy andstainless steel.
 7. The fracture fixation system of claim 2, wherein theflexible washer is made of metal having a thickness of 1 to 3 mm.
 8. Thefracture fixation system of claim 7, wherein the first and second nutseach include a body portion at the first end and a plurality of flexiblelegs extending from the body portion towards the second end of the nutsuch that the legs surround the cavity, the radially inward extendedridges being located on an inner surfaces of the legs.
 9. The fracturefixation system of claim 8, wherein the first and second nuts eachinclude four legs.
 10. The fracture fixation system of claim 2, whereinthe flexible washer is non-circular.
 11. The fracture fixation system ofclaim 10, wherein the flexible washer has two diametrically opposed ovalportions.
 12. The fracture fixation system of claim 8, wherein the bodyportion of each nut has a circumferential groove for receiving an innersurface of each washer and each washer is secured within its respectivegroove via a snap fit connection.
 13. The fracture fixation system ofclaim 2, further comprising an intramedullary nail having a bore forreceiving the longitudinally extending rod.
 14. A fracture fixationsystem comprising: a longitudinally extending rod having first andsecond ends, the first and second ends having a plurality of radiallyoutwardly extending protrusions; first and second nuts each nut having ahollow interior portion having an open end for receiving the first andsecond ends of the rod and a closed end for limiting respective movementof the first and second ends of the longitudinally extending rod, theinterior portion of the first and second nuts having a plurality ofrecesses for receiving the outwardly extending protrusions on the firstand second ends of the rod; a flexible washer mounted on the first andsecond nuts and spaced from the open end.
 15. The fracture fixationsystem as set forth in claim 14, wherein the radially outwardlyextending protrusions of the first and second rod ends are formed as ahelical thread.
 16. The fracture fixation system as set forth in claims15, wherein the radially inwardly extending recesses of the first andsecond nuts are formed as helical threads.
 17. The fracture fixationsystem as set forth in claim 14, wherein each of the nuts and respectivewashers are a one-piece construct made of a material selected from thegroup consisting of a polymeric material, titanium, a titanium alloy andstainless steel.
 18. The fracture fixation system as set forth in claim14, wherein the first and second nuts have a body portion at the firstend and a plurality of flexible legs extending from the body portiontowards the second end such that the plurality of legs surround thehollow interior portion, the plurality of recesses being located oninner surfaces of the legs.
 19. The fracture fixation system as setforth in claim 18, wherein each of the first and second nuts includefour legs.
 20. The fracture fixation system of claim 14, wherein theflexible washer is non-circular.